bitbake: codeparser/data_smart: Optimise parsing speed

The previous "contains" changes caused a ~3% parsing speed impact.
Looking at the cause of those changes was interesting:

* Use of defaultdict was slower than just checking for missing entries
  and setting them when needed.
* Even the "import collections" adversely affects parsing speed
* There was a missing intern function for the contains cache data
* Setting up a log object for each variable has noticeable overhead
  due to the changes in the code paths uses, we can avoid this.
* We can call getVarFlag on "_content" directly within VariableParse
  for a noticeable speed gain since its a seriously hot code path.

This patch therefore tweaks the code based on the above observations to
get some of the speed back.

(Bitbake rev: fca802187a2a30686a8a07d2b6b16a3e5716e293)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -35,7 +35,6 @@ import hashlib
 import bb, bb.codeparser
 from bb   import utils
 from bb.COW  import COWDictBase
-import collections
 
 logger = logging.getLogger("BitBake.Data")
 
@@ -89,7 +88,7 @@ class VariableParse:
 
         self.references = set()
         self.execs = set()
-        self.contains = collections.defaultdict(set)
+        self.contains = {}
 
     def var_sub(self, match):
             key = match.group()[2:-1]
@@ -100,7 +99,7 @@ class VariableParse:
                 varparse = self.d.expand_cache[key]
                 var = varparse.value
             else:
-                var = self.d.getVar(key, True)
+                var = self.d.getVarFlag(key, "_content", True)
             self.references.add(key)
             if var is not None:
                 return var
@@ -123,7 +122,10 @@ class VariableParse:
             self.execs |= parser.execs
 
             for k in parser.contains:
-                self.contains[k].update(parser.contains[k])
+                if k not in self.contains:
+                    self.contains[k] = parser.contains[k]
+                else:
+                    self.contains[k].update(parser.contains[k])
             value = utils.better_eval(codeobj, DataContext(self.d))
             return str(value)